Many modern operating systems executing on a computer provide a virtual area, often called a “desktop,” that serves as a user interface into which visual content such as images, icons, menus, or application user interfaces, may be drawn. The desktop, including its drawn visual content, may then be displayed onto one or more display devices connected to the computer.
A typical computer desktop may be of limited use, however, to visually impaired users, who may not be able to adequately perceive content as it is typically displayed onto a display device. Accordingly, some users use Accessibility Technology (AT) software applications, such as ZoomText™ 9.1 Magnifier/Reader, developed by Ai Squared, Inc., of Manchester Center, Vt., that facilitate visually-impaired users' use of computers. For example, such AT applications can apply enhancements, such as color enhancements, highlighting, magnification, or other enhancements, to a computer desktop to help a visually impaired user to more easily perceive displayed content. In one mode of operation, as illustrated by FIGS. 1A and 1B, an AT software application may magnify a portion (also referred to as a “viewport”) of a computer desktop 102. Viewport 106, rather than the full desktop area of desktop 102, is then displayed on display device 104. In the example of FIG. 1A, although viewport 106 includes only a portion of the full area of desktop 102, it occupies the full display area of display device 104, thereby allowing for magnification of the content in the viewport.
The boundaries defining the viewport may be adjusted, thereby allowing a user to move the viewport to magnify or otherwise enhance a different portion of the desktop. As can be seen by FIG. 1B, viewport 106 has been moved to a different portion of desktop 102. The viewport may be moved, for example, when a user causes the mouse cursor to move to the edge of the current viewport boundary, which is taken as an indication that the user desires the viewport to be moved to display visual content beyond that edge boundary. Accordingly, display device 104 shows a magnified view of the different portion of desktop 102, rather than the portion defined by the position of viewport 106 in FIG. 1A.
Another augmentative communication method that facilitates the perception of information presented on a display is closed-captioning. Closed-captioning is typically used to facilitate the perception of spoken content by hearing-impaired users. Conventional closed-captioning techniques overlay text onto visual content displayed on a display device by rendering prepared text in an opaque text box (e.g., white content on a black background). The text box may be displayed at the top or bottom of the screen or the position of the text box may change depending on the visual content that is obscured by the text box. Although conventional closed-captioning techniques obscure some of the displayed visual content, the benefit to the user in some circumstances may outweigh the fact that some of the visual content is obscured.